Understanding Multiple Long-term Chronic Conditions and Physical Disability: A Focused Review of Observational Studies

Multiple long-term conditions (MLTCs or multimorbidity) are becoming more prevalent with the aging population and are associated with poor health outcomes and quality of life, such as declined physical functions resulting in physical disability. However, limited research has examined the association between MLTCs and physical disability. Therefore, the aim of this scoping review was to summarize previous studies related to the association between MLTCs and physical disability using cross-sectional and longitudinal designs. A search was made using PubMed, Google Scholar, and Web of Science from inception to June 2024 to identify studies. Eligible studies should have defined disability and MLTCs/multimorbidity. Two reviewers independently performed the search and data extraction. The studies were categorized as cross-sectional and longitudinal designs. A total of 20 studies were included in this review. Ten studies were cross-sectional with sample sizes ranging from 100 to 31,464 participants. Ten studies were longitudinal designs with sample sizes ranging from 1751 to 16,616 participants. Age was variable across all studies ranging from 18 to 85 years with the focus on older adults in the majority of the included studies. MLTC definitions varied across studies with the majority of the studies defining MLTCs as having two or more chronic conditions. Disability definitions were different across studies with the majority reporting on activities of daily living. All of the included studies found a significant association between MLTCs and disability in cross-sectional and longitudinal studies indicating that an increased number of chronic conditions was associated with a greater level of disability. In conclusion, this study highlights that MLTCs and disability have a strong association, including over long-term follow-up. Limitations should be considered such as the definitions of MLTCs and disability that have variability across studies.